I just sold an almost identical table! Too many squares on that wall. I'd remove all of it and start over. How about a round mirror above a chest 25% wider than the mirror? Go big here or go home!

If this is a "landing zone", put a tray in the middle of the table for change, wallet, keys, etc. I would keep the items on the wall. How about color? Take inspiration from a favorite piece of fabric, accessory, or wall decor. Here's a link for ideas: https://www.houzz.com/photos/query/rustic-glam-entry-table/nqrwns

Is there a sizing rule of thumb I should go by when selecting a huge mirror? The wall is very big. That’s why I flanked this picture with the two smaller mirrors...didn’t want the artwork to look too small on the wall.

I think the main prob is the art and the mirrors above it. Deco is right. too many squares. the art, the mirrors, the glass in the door, the wainscot, the lantern,,,,,too many. try something round or softer.

I'd think about bringing the rug further back.

let me post a few examples of a console in a entry w/wainscotting and / or you type of console

I love this example. notice the rug, the styling, the art, etc.

try not to use a square mirror

this one is taller, more rectangle, and it's by itself on the wall

How about doing a few chairs on the side and one piece of art (larger than the horse) and no mirrors?

simple lamp, baskets, rug,

got for a rectangular piece of art or mirror that spans the length

The sconce idea is a good one. maybe try it for yours? but w/a decent art in the middle

Awesome advice and examples,thank you!

I agree with the suggestion of a larger base cabinet & I might center it on your ceiling fixture to avoid the air return.

I wouyld try to avoid putting that table infront of the odd vent panel, perhaps a solid skinny dresser would look better. less mirrors too. The mirror to table scale is way off.